/Engine/Source/Runtime/Engine/Classes/Engine/ReplicationDriver.h
This is the functionUNetDrivercalls to create its replication driver. It will invoke OnCreateReplicationDriver if set, otherwise will instantiate ReplicationDriverClassName from the NetDriver.
static [UReplicationDriver](API\Runtime\Engine\Engine\UReplicationDriver) * CreateReplicationDriver ( [UNetDriver](API\Runtime\Engine\Engine\UNetDriver) * NetDriver, const [FURL](API\Runtime\Engine\Engine\FURL) & URL, [UWorld](API\Runtime\Engine\Engine\UWorld) * World )